This invention relates to optical transducers.
The invention is more particularly concerned with transducers for sensing displacement using optical means.
Optical displacement transducers, for example, are well known and generally employ a light source and receiver (such as provided by the ends of fibre-optic cables), and means to vary the amount of radiation falling on the receiver in accordance with displacement. The means by which the radiation is varied may employ a movable mask with an aperture of variable size, or a neutral density filter, the density of which varies along its direction of displacement. These transducers can function satisfactorily providing that the intensity of radiation falling on the receiver is not varied for any other reason. However, any change in the radiation emitted by the light source, such as, for example, caused by variations in power supply to the light source will produce erroneous displacement readings.